This application claims the benefit of United Kingdom Patent Application No. GB0803517.2, filed on Feb. 27, 2008, which hereby is incorporated by reference in its entirety.
In the field of oil and gas exploration and production, various tools are used to provide a fluid seal between two components in a wellbore. Isolation tools have been designed for sealing an annulus between two downhole components to prevent undesirable flow of wellbore fluids in the annulus. For example, a packer may be formed on the outer surface of a completion string which is run into an outer casing or an uncased hole. The packer is run with the string to a downhole location, and is inflated or expanded into contact with the inner surface of the outer casing or openhole to create a seal in the annulus. To provide an effective seal, fluid must be prevented from passing through the space or micro-annulus between the packer and the completion, as well as between the packer and the outer casing or openhole.
Isolation tools are not exclusively run on completion strings. For example, in some applications they form a seal between a mandrel which forms part of a specialized tool and an outer surface. In other applications they may be run on coiled tubing, wireline and slickline tools.
Conventional packers are actuated by mechanical or hydraulic systems. More recently, packers have been developed which include a mantle of swellable elastomeric material formed around a tubular body. The swellable elastomer is selected to expand on exposure to at least one predetermined fluid, which may be a hydrocarbon fluid or an aqueous fluid. The packer may be run to a downhole location in its unexpanded state, where it is exposed to a wellbore fluid and caused to expand. The design, dimensions, and swelling characteristics are selected such that the swellable mantle expands to create a fluid seal in the annulus, thereby isolating one wellbore section from another. Swellable packers have several advantages over conventional packers, including passive actuation, simplicity of construction, and robustness in long term isolation applications. Examples of swellable packers are described in GB 2411918.
FIG. 1 of the drawings shows a swellable packer according to the prior art, generally depicted at 10, formed on a tubular body 12 having a longitudinal axis L. The packer 10 comprises an expanding mantle 14 of cylindrical form located around the body 12. The expanding mantle 14 is formed from a material selected to expand on exposure to at least one predetermined fluid. Such materials are known in the art, for example from GB 2411918.
As illustrated in FIGS. 2A and 2B, the dimensions of the packer 10 and the characteristics of the swellable material of the expanding portion 14 are selected such that the expanding portion forms a seal in use, which substantially prevents the flow of fluids past the body 12. FIG. 2A is a cross-section through the packer 10 located in a wellbore 20 in a formation 22. On exposure to a wellbore fluid in the annulus 24, in this case a hydrocarbon fluid, the expanding portion 14 expands and its outer diameter increases until it contacts the surface 26 of the wellbore to create a seal in the annulus 24. The seal prevents flow of fluid in the wellbore annulus between a volume above the packer 10 and a volume below the packer 10. Although shown here in use in an uncased hole, the packer 10 could of course be used in a cased hole, in which case the mantle would form a seal against the interior surface of the outer casing.
Typically a packer will be constructed for a specific application and incorporated into a casing string or other tool string by means of threaded couplings. Swellable packers are typically constructed from multiple layers of uncured elastomeric material, such as EPDM. Multiple layers are overlaid on a mandrel or tubular in an uncured form to build up a mantle of the required dimensions. The mantle is subsequently cured, e.g. by heat curing or air curing. The outer surface of the swellable mantle is then machined using a lathe to create a smooth cylindrical surface. This method produces a fully cured, unitary swellable mantle capable of sealing large differential pressures. However, the process is generally labour-intensive and time consuming, and the uncured material can be difficult to handle. Moreover, the resulting expanding portion, although robust and capable of withstanding high pressures, may be ill-suited to some downhole applications.
In wellbore construction, cement is used to seal an annulus between a casing section and an openhole, or an annulus between two concentric tubulars, to prevent undesirable fluid flow to surface. Large volumes of cement are required to seal an annulus from a casing point back to surface, and when the casing is cemented into place, the cement forms a structural component of the wellbore.
There is generally a need to provide sealing mechanisms and isolation tools and systems which may be manufactured and assembled more efficiently than in the case of the prior art, and which are flexible in their application to a variety of wellbore scenarios.
It is amongst the aims and objects of the invention to overcome or mitigate the drawbacks and disadvantages of prior art apparatus and sealing systems.
According to a first aspect of the invention there is provided a downhole apparatus comprising:
a body having a longitudinal axis and a sealing arrangement located on the body;
wherein the sealing arrangement comprises at least one elongated sealing member with an axis of elongation extending around the longitudinal axis of the body, and the sealing member comprises a material selected to expand on exposure to at least one predetermined fluid.
The axis of elongation is an axis along which the sealing member is elongated, or lengthened, with respect to the dimensions in a perpendicular axis or axes of the sealing member. In other words it is the longitudinal axis of the member.
The sealing arrangement may have an expanded condition in which an annular seal is formed. The annular seal may be formed between the body and a surface external to the body, which may be substantially concentric with the body. In this instance, the sealing arrangement may be formed on an outer surface of the body, and the seal may be in an annulus formed between the body and the surface external to the body. The surface may be the internal surface of a casing or an uncased borehole. The downhole apparatus may therefore form an annular seal, which may substantially prevent fluid flow past the body.
The downhole apparatus preferably forms a part of an isolation tool or an isolation system for sealing one region of the annulus above the apparatus from another region of the annulus below the apparatus.
The terms “upper”, “lower”, “above”, “below”, “up” and “down” are used herein to indicate relative positions in the wellbore. The invention also has applications in wells that are deviated or horizontal, and when these terms are applied to such wells they may indicate “left”, “right” or other relative positions in the context of the orientation of the well.
The body may be a substantially cylindrical body, and may be a tubular or a mandrel. The sealing member may extend circumferentially around the body. The sealing member may extend around the outer surface of the body, or may extend around an inner surface of the body.
The sealing member may form an expanding portion, which may be substantially cylindrical in form and may extend over a length of the body. The expanding portion may extend over a length of the body which is greater than the width of the elongated sealing member.
By creating a sealing arrangement from an elongated sealing member, it may be easier to assemble the apparatus when compared with conventional slip-on apparatus. For example, the expanding portion could be formed by securing a first end and a second end of the elongated member to the body at a part of the body which is axially displaced from an end of the body. For example, the apparatus could be formed on a central 2 meter portion of a 12 meter casing section.
An annular seal may be formed between the body and a surface internal to the body, which may be substantially concentric with the body. In this instance, the sealing arrangement may be formed on an inner surface of the body, and the seal may be in an annulus formed between the body and the surface internal to the body. The surface may be the outer surface of a second body, which may be a casing.
The elongated sealing member may be a strip, band, ribbon, bead, tape, rod, cable, conduit or another elongated form.
The sealing arrangement may consist of a single turn of the elongated member, but preferably comprises a plurality of turns. Preferably, the elongated member is coiled on the body.
The plurality of turns may be formed such that a lower edge of a turn is adjacent to an upper edge of a successive turn. The lower edge of a turn may abut an upper edge of a successive turn, and may create a seal with the upper edge of the successive turn. Alternatively, successive turns may be spaced from one another.
The elongated sealing member may comprise a material selected to expand or increase in volume on exposure to a hydrocarbon fluid, and which may be an EPDM rubber. Alternatively, or in addition, the elongated sealing member may comprise a material selected to expand on exposure to an aqueous fluid, which may comprise a super-absorbent polymer.
The sealing member may be formed by an extrusion process, which may be a co-extrusion of two or more materials. The two materials may both be selected to expand on exposure to at least one predetermined fluid, but may be selected to differ in one or more of the following characteristics: fluid penetration, fluid absorption, swelling coefficient, swelling rate, elongation coefficient, hardness, resilience, elasticity, and density. At least one material may comprise a foam. The material may be foamed through the addition of blowing agents. In some applications this will aid fluid absorption leading to faster swell rates and higher maximum swell volumes.
Alternatively, or in addition, the sealing member may be formed from an extrusion around a substrate.
In an embodiment the sealing member comprises one or more expanding components coupled to a core, a layer or another elongating component, which may have different physical properties to the expanding component. Advantageously the expanding component or components will at least partially encapsulate the elongating component to facilitate the provision of a seal.
The core may be a coated or uncoated cable or control line, and/or may comprise an expanding material. This embodiment has the advantage that a sealing member can be created with different properties by the combination of sheaths and cores of different designs. For example, the sheath may be used to encapsulate a core of expanding material having a different swelling characteristic to create a hybrid sealing member. The core may function as the substrate, or may be arranged to convey a fluid or a signal through the sealing member.
Alternatively, or in addition, the sealing member may comprise a substrate and means for attaching an expanding component to the substrate. The expanding component may comprise formations configured for attachment to a substrate and/or a recess for receiving a substrate. The expanding component may comprise a formation configured to receive an elongating component. The formation may be resilient and may retain the elongating component, for example by partially or fully surrounding the elongating component. The expanding component may comprise a substantially u-shaped or c-shaped profile which defines a longitudinal groove. The expanding component may comprise a clip-on member that clips around an elongating component, and may be bonded in position through the use of an adhesive or other bonding agent.
The sealing member may comprise a substrate which extends longitudinally to the member. The substrate may comprise a core, or may comprise a strip, band, ribbon, bead, tape, rod, cable, conduit or another elongated form. The substrate may comprise plastic, metal, fibrous, woven, or composite material. The substrate may function to provide structural strength to the sealing member, allow more tension to be imparted during application to a body, bind to the swellable material, resist expansion of the sealing member in a longitudinal direction, and/or resist swaging of the sealing member on the body.
The sealing member may comprise a conduit, which may be longitudinally oriented. The conduit may be formed by the substrate, or may be an open conduit. The conduit may be used to convey fluid, a cable, a control line, or a signal internally of the sealing member. The conduit may allow fluid access to the material of the sealing member from the interior of the conduit. In this way, the expansion of the sealing member may be triggered, at least in part, by fluid delivered through the sealing member.
The sealing member may couple control equipment on one side of a seal created by the apparatus to an apparatus on an opposing side of the seal. For example, the sealing member may comprise a power cable, a control line, a hydraulic line, or a data cable which runs from surface to an apparatus located below a seal created by the apparatus.
The elongated sealing member may comprise a substantially rectangular cross-sectional profile. Alternatively, or in addition, the elongated sealing member may comprise an interlocking profile, which may be configured such that a first side of the sealing member has a shape corresponding to the shape of the second, opposing side of the sealing member. The interlocking profile may be configured such that a first side of a turn of the sealing member on the body interlocks with a second, opposing side of an adjacent turn of a sealing member on the body. The interlocking profile may resist lateral separation of adjacent turns, and/or may resist relative slipping of adjacent turns. A bonding agent may be used to secure a first side of the sealing member to the shape of the second, opposing side of the sealing member. Where an interlocking profile is provided, the sealing member may be further secured through the use of an adhesive or other bonding agent.
The sealing member may have a profile configured for interlocking multiple layers of a sealing member on the body. The sealing member may have a stepped profile, a T-shaped profile or a triangular profile. The sealing member according to one embodiment comprises a flat first surface and a longitudinal spine protruding from an opposing surface. The sealing member may comprise stepped side surfaces.
The apparatus may further comprise means for securing the sealing member to the body, which may comprise a bonding agent. Alternatively, or in addition, the apparatus may comprise a mechanical attachment means for securing the sealing member to the body, which is preferably an end ring. The mechanical attachment means may be clamped onto the body, and may comprise a plurality of hinged clamping members. Alternatively, mechanical attachment means is configured to be slipped onto the body.
The mechanical attachment means may comprise a formation for receiving an end of the sealing arrangement, which may be an enlarged bore. The mechanical attachment means may comprise an engaging formation for engaging a part of the sealing member, which may be a longitudinal formation. The engaging formation may comprise teeth for engaging the sealing member. Alternatively or in addition, the engaging formation may comprise crimp portions.
In one embodiment, the engaging formation comprises threads configured to cooperate with the sealing member.
In a further embodiment, the mechanical attachment means comprises means for imparting tension into the elongated sealing member. The mechanical attachment means may comprise a ratchet mechanism. The mechanical attachment means may comprise an engaging portion, for engaging the elongated member, and a retaining portion, for retaining the mechanical attachment means with respect to the body. The engaging portion may be rotatable with respect to the retaining portion, and a ratchet mechanism may be disposed between the engaging and retaining portions.
The mechanical attachment means may comprise a release mechanism, which may be actuatable from surface and/or by a downhole intervention. The release mechanism may be actuatable to release tension in the elongated member. In one embodiment, the release mechanism is actuatable to release a ratchet. The release mechanism may comprise at least one frangible member, such as a shear pin.
In one embodiment, the mechanical attachment means is configured to be disposed on a coupling of a tubular, and may be referred to as a cross-coupling mechanical attachment means. Such a mechanical attachment means comprises an internal profile configured to correspond to the outer profile of the coupling, which may be raised with respect to the outer diameter of the tubular. This embodiment may be particularly advantageous where an expanding portion is required over the entire length of a tubular between couplings. The cross-coupling mechanical attachment means may comprise hinged clamps, swing bolt locking mechanisms, strap fasteners or other attachment means. The cross-coupling mechanical attachment may be wholly or partially cast from a metal (such as steel) or a plastic material.
The elongated member may comprise an attachment portion configured to be secured to the body. The attachment portion may comprise a formation configured to engage with mechanical attachment means of the apparatus. The attachment portion preferably comprises a termination, which may be a socket termination. The attachment portion may be crimped, bonded, screwed, or otherwise attached to the elongated member. In embodiments where the elongated member comprises a substrate, the attachment portion may be attached direct to the substrate.
The apparatus may be configured as a packer, a liner hanger, or an overshot tool.
The apparatus may be configured as a cable encapsulation assembly, and may comprise a support element disposed between the body and the sealing arrangement. The support element may be provided with a profile configured to receive a cable, conduit or other line. The support element may comprise a curved outer profile, and the assembly may define an elliptic outer profile. Alternatively the support element may comprise a substantially circular profile such that the assembly defines a circular outer profile.
According to a second aspect of the invention, there is provided a sealing member for a downhole apparatus, the sealing member comprising a material selected to expand on contact with at least one predetermined fluid, wherein the sealing member is elongated and is configured to be located on a body of a downhole apparatus such that its axis of elongation extends around the longitudinal axis of the body.
The sealing member is preferably configured to form an annular seal between a body and a surface external to the body, in use which may be substantially concentric with the body. In this instance, the sealing member may be configured for disposal on an outer surface of a body, and the seal may be in an annulus formed between the body and the surface external to the body. The surface may be the internal surface of a casing or an uncased borehole. The sealing member is therefore configured to form an annular seal, which may substantially prevent fluid flow past the body.
The sealing member may be configurable to form an expanding portion, which may be substantially cylindrical in form and may extend over a length of a body. The expanding portion may extend over a length of the body, which may be greater than the width of the sealing member.
The sealing member may be configured for disposal between a body and a surface internal to the body, which may be substantially concentric with the body. In this instance, the sealing member may be configured for disposal on an inner surface of the body, and the seal may be in an annulus formed between the body and the surface external to the body. The surface may be the outer surface of a second body, which may be a casing or an uncased borehole.
The sealing member may be a strip, band, ribbon, bead, tape, rod, cable, conduit or another elongated form.
The sealing member of the second aspect of the invention may include one or more of the optional or preferred features of the sealing member/elongated sealing member of the first aspect of the invention.
According to a third aspect of the invention there is provided a method of forming a downhole apparatus, the method comprising the steps of:                (a) Providing a body having a longitudinal axis;        (b) Providing at least one elongated sealing member comprising a material selected to expand on exposure to at least one predetermined fluid;        (c) Forming a sealing arrangement on the body by locating the at least one elongated sealing member on the body, with its axis of elongation extending around the longitudinal axis of the body.        
The method may comprise the step of forming multiple turns of the elongated sealing member on the body.
The elongated sealing member may comprise a power cable for a downhole apparatus.
According to a fourth aspect of the invention, there is a provided a method of forming a seal in a downhole environment, the method comprising the steps of:                (a) Configuring a sealing apparatus from a body and at least one elongated sealing member arranged on the body and comprising a material selected to expand on exposure to at least one predetermined fluid;        (b) Running the sealing apparatus to a downhole location such that the sealing apparatus is disposed adjacent a surface;        (c) Exposing the elongated sealing member to at least one fluid to expand it to an expanded condition, in which a seal is created between the body and the surface.        
According to a fifth aspect of the invention, there is provided method of constructing a wellbore, the method comprising the steps of:                (a) Assembling a first casing string from a plurality of casing sections;        (b) Forming at least one sealing arrangement on the casing from at least one elongated sealing member comprising a material selected to expand on exposure to at least one predetermined fluid;        (c) Running the first casing string to a downhole location;        (d) Exposing the sealing arrangement to at least one wellbore fluid, thereby expanding the sealing arrangement into contact with a downhole surface.        
The method may comprise the step of forming sealing arrangements over a majority of the length of the casing string. The downhole surface may be the surface of an openhole, or may be the surface of a downhole casing.
The method may comprise the step of running a second casing string inside the first casing string. The method may comprise the step of forming at least one sealing arrangement on the second casing from at least one elongated sealing member comprising a material selected to expand on exposure to at least one predetermined fluid.
The method may further comprise the step of exposing the sealing arrangement of the second casing to at least one wellbore fluid, thereby expanding the sealing arrangement into contact with the first casing string. The method may be repeated with third, fourth and other casing strings.
Thus the invention provides a method of wellbore construction in which a sealing arrangement formed from an elongated sealing member is located between concentric casings. Such an arrangement may be used as an alternative to cemented completions, or in conjunction with cement to provide an enhanced sealing capability.
According to a sixth aspect of the invention, there is provided a wellbore packer comprising an expanding portion formed from an elongated sealing member coiled around a body, the elongated sealing member comprising a material selected to expand on exposure to at least one predetermined fluid.
In one aspect of the invention, the sealing member is a power cable, which may be a power cable for an Electrical Submersible Pump (ESP).
According to a seventh aspect of the invention, there is provided an elongated member for forming a wellbore packer, the elongated member comprising a material selected to expand on exposure to at least one predetermined fluid.
According to an eighth aspect of the invention, there is provided a storage reel comprising a length of elongated member in accordance with any of the above aspects of the invention.
According to a ninth aspect of the invention, there is provide an overshot tool comprising a tubular body and an opening configured to be disposed over a body to be coupled in use, and a sealing arrangement arranged on the inner surface of the tubular body, wherein the sealing arrangement comprises at least one elongated sealing member with an axis of elongation extending around the longitudinal axis of the body, and the sealing member comprises a material selected to expand on exposure to at least one predetermined fluid.
The overshot tool may be configured to form part of an expansion joint. The body may be a mandrel, which may have a low friction surface. Alternatively or in addition, the body may be an end of a tubular in a downhole or subsea location.
The sixth to the ninth aspects of the invention may include one or more of the optional or preferred features of the sealing member/elongated sealing member of the first aspect of the invention.